Sensor For Detection Of Cr Research Articles

A “turn off–on” fluorescent sensor for detection of Cr(Ⅵ) based on upconversion nanoparticles and nanoporphyrin

Hexavalent chromium (Cr(Ⅵ)) is a significant environmental pollutant because of its toxic and carcinogenic properties and wide use in various industries. Hence, there is an urgent need to develop accurate and selective approaches to detect the concentration of Cr(Ⅵ) in agricultural and aquaculture products to help humans avoid potential hazards of indirectly taking in Cr(Ⅵ). In this work, we report a “turn off–on” fluorescent sensor based on citric acid coated, 808 nm-excited core–shell upconversion nanoparticles (CA-UCNPs) and self-assembled copper porphyrin nanoparticles (nano CuTPyP) for sensitive and specific detection of Cr(Ⅵ). Nano copper 5, 10, 15, 20-tetra(4-pyridyl)-21H–23H- porphine obtained by acid-base neutralization micelle-confined self-assembly method function as an effective quencher due to its excellent optical property and water solubility. Through electrostatic interactions, positively charged nano CuTPyP are attracted to the surface of negatively charged CA-UCNPs, which can almost completely quench the fluorescence emission. In the presence of Cr(Ⅵ), nano CuTPyP can discriminatively interact with Cr(Ⅵ) and form nano CuTPyP/Cr(Ⅵ) complex, which separates nano CuTPyP from CA-UCNPs and restores the fluorescence. The sensing system exhibits a good linear response to Cr(Ⅵ) concentration in the range from 0.5 to 400 µM with a detection limit of 0.36 µM. The sensing method also displays high selectivity against other common ions including trivalent chromium and is applied to the analysis of Cr(Ⅵ) in actual rice and fish samples with satisfactory results.

A water-stable pyridine bisphosphonate-based metal–organic framework as a selective and sensitive luminescent probe for Cr(VI) ions and acetone

A rare photoluminescent nitroxide pyridine bisphosphonate-based metal–organic framework, [Eu4(L)3(H2O)6]n (1) [H4L = 2,6-bis(phosphonomethyl)pyridine 1-oxide], was prepared under hydrothermal conditions and has a 3D supramolecular structure built from phosphonate linkers bridging Eu3+. It was characterized by single-crystal X-ray diffraction (SXRD), powder X-ray diffraction (PXRD), thermogravimetric analyses (TGAs), etc. The luminescence spectra of 1 show the strong characteristic luminescence of Eu3+ ions, and 1 shows high water stability, thermal stability, and chemical stability. Furthermore, luminescence studies have shown that 1 can be used as a fluorescent probe for detecting trace amounts of Cr(VI) ions and acetone in water samples with excellent sensitivity, great selectivity, and reproducibility. The detection limits are as low as 0.61 μM, 0.63 μM, and 0.0066 vol% for Cr2O7 2-, CrO4 2-, and acetone, respectively. The fluorescence quenching of 1 by Cr(VI) ions and acetone may be due to spectral overlap and absorption competition. This is the first example of a Eu-based pyridine phosphonate fluorescence sensor for simultaneous detection of Cr(VI) ions and acetone.

A blood compatible, high-efficient sensor for detection of Cr(VI) in whole blood

Fast and accurate test Cr(VI) in the whole blood is particularly critical for the treatment and prevention of Cr(VI) poisoning. Here, a blood compatible, high-efficient sensor based on the magnetic glassy carbon electrode (MGCE) that modified by conductive polyaniline (PANI), heparin and tannin modified Fe3O4 nanoparticles (magnetic tannin-modified adsorbent, MTA) with high adsorption ability toward Cr(VI) ions was developed. Results indicated the designed PANI/Hep/MTA/MGCE exhibited high sensitivity for Cr(VI) in the concentration range of 10−7 to 10−4 ppm with a 0.87 μM detection limit (3σ method). In particular, this prepared sensor not only exhibited outstanding electrochemical performance for Cr(VI) detection, but also possessed good antibiofouling characteristics due to the existence of heparin, which can provide guarantee for direct detection of Cr(VI) in the whole blood.

A highly selective multifunctional Zn‐coordination polymer sensor for detection of Cr (III), Cr (VI) ion, and TNP molecule

A new coordination polymer based on the 4‐(2,2′;6′,2″‐tripyridyl)‐4′‐1,2‐phenyl dicarboxylic acid (H2tbda), namely, [Zn (tbda)]n (1), features a one‐dimensional binuclear chain structure and exhibits the excellent luminescence in pH range of 3‐12 in aqueous solution. Particularly, compound 1 shows the remarkable selectivity, anti‐interference, and recyclability for sensing Cr (III) ion through the fluorescence enhancement. Meanwhile, compound 1 can also serve as a sensor for detecting the trace amounts of Cr (VI) ion and 2,4,6‐trinitrophenol (TNP) with high selectivity and recyclability through the fluorescence quenching effect. Furthermore, the detection mechanisms of compound 1 as a fluorescence sensor for different analytes have been explored in detail.

Linear sweep anodic stripping voltammetry: Determination of Chromium (VI) using synthesized gold nanoparticles modified screen-printed electrode

A highly sensitive electrochemical sensor has been constructed for determination of Cr(VI) with the lowest limit of detection (LOD) reported to date using gold nanoparticles (AuNPs) modified screen-printed electrode (SPE). The modification of SPE by casting pure AuNPs increases the sensitivity for detection of Cr(VI) ion using anodic stripping voltammetry. Cr(VI) ions are reduced to chromium metal on SPE-AuNPs by applying deposition potential of –1.1 V for 180 s. Afterwards, the oxidation peak current of chromium is obtained by linear sweep voltammetry in the range of −1.0 V to 0.2 V. Under the optimized conditions (HClO4, 0.06 mol L−1; deposition potential, –1.1 V; deposition time, 180s; scan rate, 0.1 V s−1), the limit of detection (LOD) was 1.6 pg mL−1. The fabricated electrode was successfully used for detection of Cr(VI) in tap and seawater. An electrochemical sensor has been constructed based on screen-printed electrode (SPE) modified with gold nanoparticles for determination of Cr(VI) ion in water samples. The coupling of anodic striping voltammetry with SPE modified nanostructures enhanced the sensitivity of electrochemical sensor for detection of Cr(VI) ion at low sample volumes.

Ratiometric Detection of Cr3+and Hg2+by a Naphthalimide-Rhodamine Based Fluorescent Probe

Newly synthesized rhodamine derivatives, L(1) and L(2), are found to bind specifically to Hg(2+) or Cr(3+) in presence of large excess of other competing ions with associated changes in their optical and fluorescence spectral behavior. These spectral changes are significant enough in the visible region of the spectrum and thus, allow the visual detection. For L(1), the detection limit is even lower than the permissible [Cr(3+)] or [Hg(2+)] in drinking water as per standard U.S. EPA norms; while the receptor, L2 could be used as a ratiometric sensor for detection of Cr(3+) and Hg(2+) based on the resonance energy transfer (RET) process involving the donor naphthalimide and the acceptor Cr(3+)/Hg(2+)-bound xanthene fragment. Studies reveal that these two reagents could be used for recognition and sensing of Hg(2+)/Cr(3+). Further, confocal laser microscopic studies confirmed that the reagent L(2) could also be used as an imaging probe for detection of uptake of these ions in A431 cells.

Enhanced ultrasensitive detection of Cr(III) using 5-thio-2-nitrobenzoic acid (TNBA) and horseradish peroxidase (HRP) dually modified gold nanoparticles (AuNPs)

In this study, an enhanced ultrasensitive and selective sensor for detection of Cr(III) was constructed based on gold nanoparticles (AuNPs) dually labeled with 5-thio-2-nitrobenzoic acid (TNBA) and horseradish peroxidase (HRP). TNBA was used as an affinity tag for Cr(III) binding and HRP as optical signal amplifier. Following the addition of Cr(III), the aggregation of AuNPs labeled with TNBA occurred, because the nitryl groups of TNBA selectively interacted with Cr(III). After the addition of TMB solution to the aggregation, the optical signals would be generated. The density of the signal is correlated with the concentration of Cr(III), which can be easily discerned by the naked eye or be measured spectrophotometrically. The application results indicated that the dually labeled sensor (TNBA–AuNPs–HRP) was highly sensitive to Cr(III) in the concentration of 0.04 to 210 μM. The limit of detection (LOD) was 0.04 μM, which is 45 times lower than that of the sensor without HRP enhancement.